Watercraft, especially those of the type known as personal watercraft, are commonly powered by internal combustion engines positioned within their hulls. These engines are arranged to drive a water propulsion device for propelling the craft.
The engine typically has at least one cylinder in which is movably mounted a piston. The piston is connected to a crankshaft which is mounted for rotation with respect to the remainder of the engine. Combustion of fuel within the cylinder moves the piston, which in turn effectuates rotation of the crankshaft.
As is well known, it is generally undesirable for the speed of the engine to exceed a predetermined high speed. The engine speed is normally measured by the number of revolutions per minute which the crankshaft turns.
In order to limit the engine speed, a number of engine speed or "rev" limiting arrangements have been proposed. In a common arrangement, the ignition firing timing is delayed (i.e. retarded) so that less time is provided for combustion in the cylinder before the exhaust cycle. Unless the ignition firing timing is substantially delayed to the point where misfiring is occurring, this method of limiting the engine speed is not always particularly effective. In addition, the exhaust system associated with many watercraft engines includes an exhaust catalyst. When the ignition firing timing is delayed, continued combustion may occur in the exhaust system when a combusting air and fuel mixture is exhausted, damaging the catalyst.
In another arrangement, the ignition system for the engine may be shut off. In this arrangement, the ignition elements do not fire, preventing combustion in the cylinders. This arrangement has the detriment that the engine is stopped as the engine speed exceeds a predetermined speed, and once the engine speed falls below the predetermined speed it is again started but may need to immediately be shut off again as the engine speed surges higher. This fluctuation between engine operation and nonoperation results in very rough watercraft operation for the rider.
An improved engine speed or "rev" restriction system for an engine powering a watercraft is desired.